The invention relates to outboard marine propulsion units, and more particularly to the sealing structure between the water tube from the cooling sea water pump adn the adapter plate mounting the power head including an internal combustion engine.
An outboard marine propulsion unit has a lower gearcase with side openings supplying cooling sea water to a water pump driven by a vertical drive shaft in the gearcase. A water tube extends upwardly from the water pump to an adapter plate at the top of the gearcase which mounts the powerhead including the internal combustion engine. The adapter plate has a water passage supplying cooling sea water therethrough from the water tube to the powerhead. The sealing fittings connected the water tube to the adapter plate have been subject to leaking after certain assembly steps, particularly oven painting, which in turn has required that the mounting bolts for the fitting be retorqued.
The present invention provides improved sealing structure for connecting the water tube to the adapter plate which is particularly simple and easy to assemble, and solves leakage problems. The invention also maintains insulation between a copper water tube and an aluminum adapter plate to prevent a chemical reaction between the two.